Cancer of the breast is the most common cause of cancer death in middle aged women in Europe and North America and both its incidence and mortality are on the increase (1-5). The predominant indications for breast tumor imaging are: detecting the presence of tumor, localizing sites of disease, and following the effects of therapy (6). Trends in scintigraphic imaging have been towards developing imaging pharmaceuticals to provide quantitative information on the pathophysiological characteristics of a tumor, such as its anaplasticity, or likely response to a given therapy (7). For example, to determine via scintigraphic imaging how a patients breast cancer will respond to the administration of a growth suppressor, such as somatostatin, or the estrogen receptor antagonist tamoxifen (8 Diamandis in PCT Application CA 94/00267 has shown that the presence of PSA in breast tumors, as measured by in vitro methods, has prognostic value. Thus, imaging of these tumors may not only reveal occult disease, but may also provide clinically valuable pathophysiological information.
Tumor imaging is commonly carried out using a gamma emitting radionuclide conjugate and a scintillation gamma camera, or with a positron emitting radiopharmaceutical and a positron or PET camera, or with a magneto-pharmaceutical and a magnetic resonance imaging device. The scintillation camera, also known as an Anger camera, consists of a detector head, and a display console. The Anger camera head is composed of sodium iodide crystals that absorb gamma rays and emits the absorbed energy as flashes of light--scintillations that are proportional in brightness to the energy absorbed. In a gamma camera the sodium iodide crystals are coupled to photomultiplier tubes that convert light pulses into electronic pulses. These voltages are translated via a computing circuit to a cathode ray tube. The data from the camera head may be in either analog or digital form that can be stored in a computer and can reconstruct the data to provide an image. Single-photon emission computed tomography (SPECT) imaging involves the use of a gamma scintillation camera where multiple images, typically encompassing 180.degree. or 360.degree., around the body are taken and the computer issued to reconstruct multiple tomograms in coronal, sagittal, and transverse projections. In PET imaging the positron radionuclide collides with an electron causing annihilation of the particles and creating two photons that travel in 180.degree. opposite directions. The PET system is designed to capture opposite sides and register the count at precisely the same time. A computer is used to manipulate the data and then reconstruct a cross sectional image from this information.
There are a number of approaches to breast tumor imaging that may be divided into two groups: indirect and direct. Indirect techniques, are generally utilized to locate metastatic disease by recognizing the secondary effects of tumor within an organ system. Indirect techniques include, but are not limited to, the use of radiolabelled .sup.99m Tc phosphonates to locate bone metastases (9,10) and .sup.99m Tc radiocolloids in liver scans and breast lyphoscintigraphy (11,12,13).
Direct approaches to radionuclide imaging include radiolabelled chemotherapeutic agents, simple ionic substances, metabolite imaging, immunologic and receptor imaging. The use of radiolabelled chemotherapeutic agents, such as bleomycin, have not demonstrated clinical value (14). .sup.67 Ga citrate is the most commonly used simple ionic tracer for tumor imaging, however it localizes in other pathologies and is non specific (15,16,17,18). Metabolite imaging carried out with positron emitting radionuclides such as .sup.18 F-fluorodeoxyglucose, .sup.11 C-methionine and .sup.11 C-thymidine provides tumor metabolism information that has been shown to be clinically valuable for disease staging (19,20,21).
The receptor imaging of breast cancer has been attempted by several approaches. Spicer et al. (22) and Hochberg (23) and others (24-29) have developed radiolabelled estradiols and have been able to demonstrate imaging in estrogen receptor positive breast cancers. It has been postulated that a therapeutic response could result with Auger electrons from .sup.123 I or .sup.125 I radiolabelled estradiols(30,31), or from .beta. emitting radioisotopes such as .sup.186 Re conjugated to progesterone (32). A problem with receptor based imaging is the interference that estrogen receptor antagonists, such as tamoxifen, may have in the clinical environment.
It is known that proteins, such as antibodies, can be developed against specific antigens that are either produced or associated with tumors, can be used to localize tumors. U.S. Pat. No. 3,927,193 to Hansen et al. (33) discloses a process whereby antibodies to carcinoembryonic antigen (CEA) and labelled with .sup.125 I and .sup.131 I were used to image the location of tumors present in hamsters. From this work it was proposed that the location of a tumor in a human could be determined by in vivo administration of a parenteral solution containing an antibody-radioisotope conjugate followed by imaging by a gamma camera. Goldenberg et al. reported success in clinical trials of tumor detection and localization by scintillation scanning of patients that received radiolabelled antibodies to CEA (34).
Based on the original work of Milstein and Kohler (35), monoclonal antibodies have been developed against a variety of tumour antigens such as CA 19.9, CA 125, melanoma associated antigens, TAG 72, .varies. fetal protein, ferritin, choriogonadotropin, prostatic acid phosphatase, and PSA for radioimmunoimaging and therapy.
Several investigators have reported on the development of monoclonal antibodies against epitopes of various malignant prostate cell components (36,37,38,39,40). Moreover, PSA was purified and well characterized and found to have a molecular weight in the range of 34,000 (41). PSA is used widely as a tumor marker for in vitro based analyses for diagnostic and monitoring purposes of prostatic carcinoma. U.S. Pat. No. 5,162,504 describes monoclonal antibodies that have been developed to recognize malignant prostate epithelium. These antibodies were developed as diagnostic and prognostic tools for the detection of cancer of the prostate, not as embodied in this invention, for the detection of cancers not associated with the prostate. Until the discovery reported by Diamandis in International Application PCT CA94/00267, it was thought that PSA only occurred in men and was only produced by prostate tissue.
To image breast tumors researchers have developed antibodies directed against TAG 72, CA-3, CEA, EGF-R, LASA-P, and other glycoproteins associated with breast cancer (42,43,44). Khaw et al. developed the monoclonal antibody 323/A3 against a 43 Kd membrane associated glycoprotein from the MCF-7 tumor cell line that was able to image tumors as small as 0.19 grams (45). Rainsbury et al. developed the antibody LICRCON-M8 against human milk fat globule and were also able to demonstrate imaging of human breast tumors, of particular note metastases to the bone were found (46).
Antibodies have been labelled directly with radioisotopes such as .sup.123 I, .sup.125 I, .sup.131 I, .sup.18 F, .sup.186 Re, .sup.188 Re, and .sup.99m Tc and indirectly with chelating complexes such as diaminetrimethylenepentaacetic acid using .sup.111 In, .sup.90 Y, .sup.99m Tc, .sup.186 Re and .sup.188 Re (47,48). Antibody-mediated radiotherapy may be carried out using either beta emitting radionuclides such as .sup.186 Re, .sup.188 Re, .sup.131 I, .sup.90 Y, .sup.153 Sm, .sup.32 P or .sup.109 Pd, or with alpha particle emitters such as .sup.211 At or .sup.212 Pb, or with Auger electron emitters such as .sup.125 I or .sup.123 I (47,48). Therapy may also be attempted with either drug or toxin based conjugates for example Adriamycin-immunoconjugates (49) and vinblastine-immunoconjugates (50) have been developed. An unexpected finding of the clinical usefulness of immunoscintigraphy has been the reported complete remission of 7 out of 10 FIGO IV ovarian cancer patients who under went repeated imaging with an OC 125 antibody and had anti-idiotypic HAMA (51).
Magnetic resonance imaging can be carried out using gadolinium and other lanthanides or metals such as iron conjugated to antibody based proteins. Several versions of these antibody based products are believed to be undergoing clinical evaluation and commercial development presently.
To improve the specific activity and safety of the immunoconjugate directed towards tumor markers several approaches have been taken ranging from the use of antibody fragments to genetic engineering of recombinant produced humanized antibody constructs to synthetic peptides based on the antibody epitope (52,53). Methods of antibody engineering including single chain antibodies have been well summarized by Borrebaeck (54). These improvements have improved the tumor target to background ratio and reduced the incidence of human antimouse antibody response.
The present invention provides a method for detecting, locating and treating non-prostatic endocrine tumors involving PSA as the tumor marker and optionally further optionally improves this method by first priming the endocrine tumors to produce PSA.